In recent years, with increasing performance of electronic devices or communication devices, the speed of serial transmission between devices has continued to increase. When the quality of a device supporting such high-speed serial transmission is evaluated, it is necessary to transmit a digital signal at a high bit rate to a measurement device while suppressing deterioration of a waveform.
For example, a device that measures an error rate of a digital signal transmits and receives a high-speed pulse pattern signal such as a pseudo-random bit sequence to and from a device under test (DUT) via a transmission line.
A transmission line functions as a low pass filter with respect to a high-speed signal to greatly attenuate high-frequency components of a signal that is propagated via the transmission line. Therefore, a technology for lifting up the high-frequency components relative to low-frequency components using an equalizer in order to compensate for the high-frequency components lost due to low-pass filter characteristics of the transmission line is conventionally known (for example, see Patent Document 1).
However, the equalizer disclosed in Patent Document 1 is unable to support a wide range of bit rate since the equalizer is a passive equalizer. Therefore, when signals at various bit rates output from the DUT are measured, a plurality of equalizers having pass characteristics according to the bit rates are prepared and required to be switched between and attached to a measurement device one by one.
A method of configuring a plurality of equalizers having different pass characteristics in parallel using a high-frequency switch (see, for example, Patent Document 2) that switches between and connects a plurality of individual terminals to one common terminal, and switching between a plurality of equalizers may be considered. However, since the switching element is used in the high-frequency switch disclosed in Patent Document 2, an insertion loss is caused by this switching element.
Meanwhile, an equalizer capable of changing a peak frequency of equalizer characteristics without using a switching element has been proposed (see, for example, Patent Document 3).